This application relates to the art of cabinets for enclosing electrical equipment and, more particularly, to fire suppression arrangements for such cabinets. The invention is particularly applicable to electronic chassis or shelf units for supporting telecommunications equipment and will be described with particular reference thereto. However, it will be appreciated that the invention has broader aspects and that features thereof may be used for other purposes in other environments.
Standard requirements for Network Equipment Building Systems are published by Telcordia for telecommunications equipment, and one of the requirements is fire resistance. In the event of a fire within a cabinet that encloses telecommunications equipment, it is both desirable and necessary to prevent the fire from spreading to other equipment, to suppress the fire and to ensure that the fire quickly is extinguished. It would be desirable to have an improved arrangement to satisfy the fire resistance requirements for Network Equipment Building Systems.
A cabinet in accordance with the present application includes a perforated top panel through which ventilation air normally flows. The inner surface of the perforated top panel is coated with intumescent material which expands at an elevated temperature to close the ventilation openings in a localized area that is influenced by a flame to block the flame against extending through the top panel and thereby prevent spread of the flame, along with inhibiting flow of ventilation air to the source of the fire.
In one arrangement, the top panel has circular holes that provide the ventilation openings and the peripheral surfaces of the holes as well as the inner surface of the top panel are coated with an intumescent material.
In accordance with another aspect of the invention, metal fire plates are positioned between adjacent printed circuit boards to prevent fire from spreading from one circuit board to another. In one arrangement, the fire plates are attached to one side of printed circuit boards in outwardly-spaced relationship thereto. The fire plates are positioned on the side of the printed circuit board that contains electronic components.
In a preferred arrangement, the fire plates are attached to the printed circuit boards by standoff snap fasteners that snap through holes in the printed circuit boards and hold the fire plates in outwardly-spaced relationship to one side of the printed circuit board.
The flame suppression cabinet of the present application includes a shelf rack for supporting a plurality of printed circuit boards that lie in vertical planes and are spaced-apart in a direction between the cabinet sides. Equipment mounted within the cabinet is of the type for linking a Central Office switch and optical network of a telecommunications service provider with individual users of the service. Equipment of the type with which the present invention may be used includes, but is not necessarily limited to, DISC*S channel shelf, DISC*S common shelf, MX MDS shelf and HDD shelf. DISC*S is a registered trademark of Marconi Communications, Inc. Obviously, the invention can be used for any type of cabinet in which electronic equipment is enclosed and through which ventilation air normally flows.
It is a principal object of the present invention to provide an improved flame suppressing cabinet for enclosing electronic equipment.
It is another object of the invention to provide an improved fire suppression plate arrangement for printed circuit boards.
It is also an object of the invention to provide a cabinet for telecommunications equipment that meets or exceeds the fire resistance requirements that are promulgated by Telcordia for Network Equipment Building Systems.